In an extensive blog post, Monty said that the so-called "open core" model – where open source code is sold alongside proprietary add-ons – was not the original intention of MySQL and that the setup devalues the open source project. The full open source nature of the project was what made MySQL so popular, he explains, and Sun’s earlier attempts to move to an open core model were squashed.

“When Sun bought MySQL, and the shareholder agreement expired, they saw their chance and announced that backup would be a commercial closed source extension,” he said.

“This initiative was however quickly killed by Sun's management who did understand the true value of MySQL as an open source project and by making it closed source they would have made it less valuable.”

The original MySQL did not need an open core model, Widenius said, because it was an infrastructure product that could be licensed to others who wished to embed it into other products. Furthermore, he accused Oracle of selling extensions that it didn’t even develop. Some of the thread enhancements being sold were developed by eBay and contributed to the code base.

However, Monty did point out that the same the threading technology was available to users of MariaDB, and the rest of the features Oracle is selling around MySQL could also be replicated in an open source manner. ®